Appendix D — Pathology & Image Appearance Reference
Purpose
This appendix provides a reference guide to common pathologies that affect subject contrast and may require adjustments to radiographic technique. It is organized by anatomical region to match the textbook sequence, helping students and clinical preceptors recognize when changes in tissue density, composition, or distribution impact exposure decisions. By understanding how pathology alters normal contrast relationships, learners can improve image quality, reduce repeat rates, and ensure diagnostic accuracy across a range of clinical scenarios.
Technique Strategy: When adjusting technique for pathology, consider whether the condition increases or decreases tissue density. Increased density (e.g., fluid, bone sclerosis) typically requires higher kVp or mAs, while decreased density (e.g., air, bone loss) may benefit from reduced exposure. Always tailor technique to the patient’s body habitus and clinical presentation.
Pathologies Requiring Technical Factor Adjustments
| Region / System | Pathology | Effect on Subject Contrast | Recommended Technique Adjustment |
|---|---|---|---|
| Thorax | Pneumothorax | Increased radiolucency due to air in pleural space | ↓ mAs slightly to avoid overexposure |
| Thorax | Pleural Effusion | Increased density from fluid accumulation | ↑ mAs or kVp moderately for penetration |
| Thorax | Pneumonia | Patchy consolidation reduces beam transmission | ↑ mAs moderately |
| Thorax | Emphysema / COPD | Hyperaeration increases radiolucency | ↓ mAs slightly |
| Abdomen | Ascites | Increased soft tissue thickness from fluid | ↑ mAs or kVp; consider grid use |
| Abdomen | Bowel Obstruction | Increased air contrast in dilated loops | ↓ kVp to enhance air–soft tissue differentiation |
| Musculoskeletal | Osteoporosis | Decreased bone density; reduced attenuation | ↓ kVp and mAs to avoid overexposure |
| Musculoskeletal | Osteopetrosis | Increased bone density; sclerotic appearance | ↑ kVp and mAs for adequate penetration |
| Musculoskeletal | Paget’s Disease | Thickened, sclerotic bone with mixed density | ↑ kVp; adjust mAs based on region |
| Musculoskeletal | Joint Effusion | Increased soft tissue thickness around joint | ↑ mAs or kVp to penetrate fluid |
| Musculoskeletal | Fractures with Hardware | Metal increases attenuation; soft tissue may be obscured | ↑ kVp and mAs; use grid to maintain contrast |
| GI | Double-Contrast Studies | Air and barium create high subject contrast | ↓ kVp (90–100); short exposure time |
| GI | Post-Surgical Abdomen | Altered anatomy; possible fluid or air pockets | ↑ mAs or kVp; tailor to patient habitus |
| GU | Obesity / Edema | Increased soft tissue thickness | ↑ mAs or kVp; grid recommended |
| GU | Residual Urine / Bladder Distention | Fluid-filled bladder increases density | ↑ mAs moderately |
| Head | Sinusitis | Fluid levels and mucosal thickening | ↑ kVp; horizontal beam for air–fluid levels |
| Head | Orbital Fracture | Disruption of bony margins; possible air–fluid levels | ↑ kVp for bone detail; ↓ mAs for soft tissue |
| Head | Neoplasm | Variable density; may obscure normal anatomy | ↑ kVp; careful collimation to reduce scatter |
| Pediatrics | Pediatric Pneumonia | Consolidation with smaller thoracic volume | ↑ mAs slightly; use short exposure time to reduce motion |
| Pediatrics | Congenital Heart Disease | Enlarged cardiac silhouette; increased vascular markings | ↑ mAs or kVp; ensure full inspiration and proper centering |
Congenital Anomalies
Congenital anomalies may alter normal anatomy, tissue density, or positioning requirements, impacting subject contrast and image quality. This section highlights common congenital conditions that require radiographic technique adjustments to ensure diagnostic accuracy and patient safety. Awareness of these variations is essential for adapting exposure factors and positioning strategies, especially in pediatric imaging.
| Region / System | Congenital Anomaly | Effect on Subject Contrast | Recommended Technique Adjustment |
|---|---|---|---|
| Musculoskeletal | Osteogenesis Imperfecta | Decreased bone density; fragile cortices | ↓ kVp and mAs; avoid compression; gentle immobilization |
| Musculoskeletal | Achondroplasia | Abnormal bone shape and metaphyseal thickening | ↑ kVp for dense regions; adjust centering and collimation |
| Musculoskeletal | Clubfoot | Small, rotated bones; altered joint alignment | ↓ kVp for pediatric bone; oblique views; careful positioning |
| Musculoskeletal | Polydactyly / Syndactyly | Extra or fused digits; overlapping structures | ↓ kVp for pediatric bone; tight collimation; oblique/lateral views |
| Spine & Pelvis | Spina Bifida | Incomplete vertebral arch; soft tissue mass | ↓ kVp for soft tissue contrast; careful collimation |
| Spine & Pelvis | Hemivertebra / Congenital Scoliosis | Asymmetric vertebral density; uneven tissue thickness | ↑ kVp for uniform penetration; compensating filters; stitching |
| Pelvis | Developmental Dysplasia of the Hip | Shallow acetabulum; displaced femoral head | ↓ kVp for pediatric bone; frog-leg or neutral AP pelvis |
| Head | Craniosynostosis | Abnormal skull shape; fused sutures | Adjust CR angle and collimation; multiple projections |
| Head | Cleft Palate | Thin bone; altered oral/nasal anatomy | ↓ kVp for bone detail; modified Waters; avoid superimposition |
| Head | Hydrocephalus | Enlarged ventricles; thin calvarium | ↓ kVp for soft tissue/CSF contrast; avoid overpenetration |
| Head | Down Syndrome | Flat occiput; atlantoaxial instability | ↓ kVp for thin bone; avoid excessive neck flexion/extension |
| GI / GU | Malrotation / Situs Inversus | Abnormal organ position; altered soft tissue contrast | Reposition for anatomy; adjust technique for organ overlap |
